Some people are never on time, and it seems some planets have the same problem. Yale astronomers, along with Planet Hunters, a team of citizen scientists, recently discovered a new planet that has issues with punctuality.
This new planet called PH3c, which has a low density and low mass, is 2,300 light years from Earth. The atmosphere of the planet is mostly hydrogen and helium.
Because of PH3c's odd schedule, astronomers initially missed it. However, Planet Hunters discovered its existence after poring over data from NASA's Kepler mission.
Kepler's data has already confirmed over 900 planets. Now, we can add PH3c to the list.
PH3c has a unique orbit that's inconsistent and doesn't seem to operate on a schedule. Astronomers believe this is because of the gravitational pull from other planets in the system.
Such gravitational forces are usually small, but this system is different. PH3c's orbital cycle changes over 10 hours in about every 10 orbits. In comparison, if PH3c were Earth, this year might be 365 days long, but 10 years later, the year would be just over 367 days long.
This weird orbiting cycle prevented computer algorithms from discovering the planet, but human eyes picked up a third transit signal from this system. Transit happens when planets cross in front of their stars, creating a signal, or a "blink" in light when looked at.
PH3c's star is young. The system contains two other planets, with orbital cycles of 35 and 126 days, with the outermost planet being a gas giant. The discovery of PH3c allowed astronomers to measure the mass of the other two planets, based on when they transited in front of their star.
"Finding the middle planet was key to confirming the others and allowing us to find their masses," says Joseph Schmitt, a Yale graduate student. "The outer planet's orbital period also changes slightly, by about 10 minutes. You need to see both planets' changing orbital periods in order to find out the masses of the planets. One planet doesn't give enough information."
PH3c is a little over twice the size of Earth, but its mass is at least four times greater. This suggests that its composition is mostly hydrogen and helium. The outer planet is probably a lot like Saturn. The third planet is likely rocky, similar to Earth.
Planet Hunters consists of over 300,000 citizen scientists, all volunteers, looking over scores of data collected by Kepler.
"It harnesses the human dimension of science," says Debra Fischer, Yale lead of the exoplanets group. "Computers can't find the unexpected, but people can, when they eyeball the data."
